Railway signaling



April 23, 1929. v, w s 1,710,497

RAILWAY S I GNALING Filed Sept. 21, 1916 4 Sheets-Sheet- 1 NYENTOR W WZQM 1 AM im April 23, 1929. v, EW 1,710,497

RAILWAY SIGNALING Filed-Se t. 2 1. 1 16 4 Sheets-Sheet 2 WITNESSES April 23, 1929. v gw s 1,710,497

RAILWAY S IGNALI NG F1195 Sept. 21, 1916 4 Sheets-Sheet 3 gqh 8 I B R FIG-4 WITNESSES INVENTOR April 23, 1929. v, Ew s 7 1,710,497

RAILWAY S IGNALING Filed Sept. 21. 6 4 Sheets-Sheet 4 g Q Y E m w a a Q Q! 3 B \9 WITNESSES INVENTOR Patenge'd A injzs, 1929'.

UNITED STATES- PATENT. OFFICE.

LLOYD V. LEWIS, OFEDGEWOOD BOROUGH, PENNSYLVANIA, ASSIGNOR 1'0 THE UNION SWITCH & SIGNAL COMPANY, OFSWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

RAILWAY SIGNALING.

Application filed September 21, 1916.. Serial No. 121,377.-

My invention relates to railway signaling, and particularly to signaling of the'type in which alternating current, preferably of high frequency is employed in the track rails for the purpose of controlling traflic thereover.

I will describe certain forms of signaling systems and apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing one form of signaling system embodying my invention. Fig. 2 is a diagrammatic view showing a modified arrangement of the vehicle-carried receiving circuit shown in Fig. 1". Fig. 3 is a diagrammatic view showing one arrangement of speed governing apparatus which may beemployed in conjunction .with the relays shown on the vehicle in Figs. 1 and 2. Fig. 4 is a view similar to Fig. 1 but showing a modification thereof also embodying my invention. Fig. 5 is a view similar to Fig. 3 but showing an adaptation of the speed controlling apparatus to the system of Fig. 41 Fig. 6 is a view showing one form of apparatus for transforming a low frequency current into one of high frequency at or near the point at which the current is to be impressed upon the track rails; Fig. 7 is a diagrammatic view showing a-further modified form of the signaling systems shown inFigs. 1 and 4.

Similar reference characters refer to similar-,parts breach of the several views.

Referring fi rst to Fig. 1, the reference characters H and H designate tlie track rails of a railway along which cars or trains normally move in the direction indicated by the arrow. The .railway is divided into block sections A-B, B-C, etc, by any suitable means which, as here shown, are insulated joints 2 in the rail H. The other rail H being electrically continuous it'may,

if the propulsion energy for the cars is elec-.

tricity, be included in the circuit for the propulsion current in the usual or well 1 It 1s immaterial toxthe presentmvention, however, how the segreknown manner.

nating signaling currents differing. in frequency. As here shown, two such currents are employed, and as shown in-Fig. 1, they are supplied from two pairs of transmission mains 3 and 3, which pairs are connected respectively .with two generators 4 and 4 of high frequency currents differing in frequency. The frequencies of these currents may be, for example, 7,000 and 10,000 cycles per second, although it is understood that the frequency values may be radically diiferent from those given as examples without departing from the scope of my. invention. For each section I provide two transformers T and T, the primaries of which are connected respectively with transmission mains 3 and 3, and the secondaries of which are connected with the track rails of the section adjacent the exit .end thereof. Connected in series with the primaries of each of the transformers T-is a condenser 5 which serves to balance the reactance of the circuit and t us to reduce the impedance of the circuit to a minimum to currents of the frequency of generator 4, that is, the pri-' mary circuit of transformer T is tuned to resonance. Similarly, condenser 5 is con For eachblock section I provide means Y for impressing on the rails thereof alternected in series with the primary of transformer-T in order to reduce the impedance of this circuit to a minimum to currents of the frequency of generators 4; The secondary of each transformer T is connected directly across the rails, and connected in connected in series with the condenser 6 to form a circuit resonant with the respective primary, the supplyof current from each transformer T to the rails of the corresecondary-of each transformer T. is also sponding section being controlled by the condition of trafiic in the section next in advance, as T will hereinafter explain.

Located adjacent the entrance end of each block section is a relay S adapted to respond to current of the frequency supplied to the rails by transformer T. This relay is connected in a circuit including the secondary of a step-up transformer 7 and a condenser 8, which circuit is tuned to resonance at the frequency of the current delivered by transformer T. The primary of transformer 7 is connected across the track rails of the section and in series therewith is a condenser 9, this condenser and the transformer primary forming a circuit tuned to resonance at the frequency of the current delivered by transformer T. It will be seen, therefore, that in any one block section the resonant circuit comprising condenser 6 and the resonant circuit comprising condenser 9 are coupled together by the rails of the section, so that if such section is unoccupied and the rails thereof are intact throughout, current of the frequency of generator 4 is supplied to transformer 'Z and so to the relay S and this relay is therefore energized.

As stated hereinbefore, the supply of energy from each transformer T to the rails of the corresponding section is controlled by traflic conditions in the section next in advance. As here shown, this is accomplished by a contact 10 of the relay S for the block in advance, which contact is closed only when relay is energized. It will be-seen', therefore, that current from any transformer T is supplied to the rails of the corresponding section only when the section next in advance is unoccupied and the rails thereof are intact.

In Fig. 1 T have shown adjacent the entrance end of each block section a second relay S responsive to current of the frequency supplied by generator 4 and transformer T. This relay S is necessary only in case fixed or roadside signals are desired; in the event that such signals are not provided, this relay can be dispensed with. Relay S is connectedwith the track rails in the same manner as relay S, except that the circuit comprising condenser 8 and the secondary of transformer 7 and the circuit comprising the primary of this transformer and condenser 9, are resonant to current of the frequency delivered by generator a and transformer T.

Inasmuch as relays S and S are connected with the track rails through the medium of circuits resonant to the frequencies of transformers T and T, respectively, it is obvious that these relays will respond selectively to currents of these two frequencies, that is, neither relay will be energized unless current of the frequency to which its associated circuits are tuned is present.

In Fig. 1 T have shown fixed or roadside signals F, F, etc., but the provision of such signals 'is not essential for the reason that the passage of cars or trains along the railway may be adequately governed by the signals and other apparatus on the cars or trains themselves, as hereinafter described and explained. One fixedsignal device is located adjacent the entrance end of each block section, and as here shown, each of these signals is of the well known light type comprising three electric lamps G, Y and R, indicating, when illuminated, proceed, caution and stop, respectively. These several indications are usually conveyed by green, yellow and red glass in front of the respective lamps, as is well understood in the art. These lamps are controlled by relays S and S through the medium of circuits supplied with current from a suitable source, such as a battery 11. These circuits need not be traced in detail, it being sufficient to point out that lamp G is controlled by the upper point of contact 12 of relay S and the upper point of contact 13' of relay S so that this lamp can be illuminated only when both relays are energized, that is, when the corresponding block section and the section next in advance are unoccupied; lamp Y is controlled by the upper point of contact 12 of relay S and the lower point of contact 18 of relay S so that this lamp is illuminated only when relay S is energized and relay S de-energized, that is, when the corresponding block section is unoccupied and the section next in advance is occupied; and lamp R is controlled only by the lower point of contact 12 of relay S so that this lamp is illuminated only when this relay is de-energized, that is, when the corresponding section is occupied by a car or train.

At the left of the drawing I have shown diagrammatically a railway vehicle V (a car, locomotive or train) which is equipped with apparatus adapted to be controlled by the signaling currents in the track rails and which apparatus is arranged to give signal indications by virtue of which the speed or progress of the vehicle are governed. As here shown, the signaling apparatus comprises three lamps, G, Y and R, which lamps are used to give the same indications as those in the roadside signals, viz, proceed, caution 'and stop. The signal lamps on the vehicle are controlled by two relays P and P also carried on the vehicle,

and this control is exactly the same as the control of the lamps, in any one of the roadside signals by the corresponding roadside relays S and S. The relays P and P are responsive to the high frequency signaling currents, and are controlled by these currents in the manner which I will now explain.

Mounted on the vehicle V in front of the forward pair of wheels is a coil 14 which is in inductive relation to the forward axle and to a short section of both of the track rails in advance of that axle. Across the terminals of coil 14 is connected a condenser 15, coil 14 and condenser 15 comprising a closed circuit a tuned broadly to the mean of the two frequencies'of generators 4 and 4.

Inasmuch as the currents which flow in this circuit are very feeble and are therefore unsuitable to operate relays constructed with sufficient ruggedness for commercial purposes, I interpose between the circuit and the relays a current amplifying device K, which I will now describe.

Theamplifying device K comprises a I vacuum tube or bulb 16 having mounted therein a filament 17, preferably of tungsten,

a metallic plate 19, and a metallic grid 18 interposed between the filament and the plate. The filament 17 is constantly heated by a battery 20, and the terminals of coil 14 and condenser 15 are connected by wires 21 and 22 respectively with the grid 18 and one terminal of the filament 17 so that the alternating currents in the resonant circuit a produce an alternating difference of potential between the grid and the filament. A. battery 23 is connected with the filament 17 and the plate 19 in such direction that a flow of current through the tube or bulb will result,

owing to the electron emission from the heated filament 17. The oscillating differ- .ence in potential between the grid and the filament serves to increase and decrease the i rate of emission of electrons from the filament and hence produces corresponding variations in the strength of current flowing in the circuitof battery 23. The circuit of battery 23 includes the primaries of transformers 25. and 25? across whose terminals is connected condenser 24 to tune the transformer circuit broadly to the mean of the two frequencies of generators 4 and 4. The secondaries of these transformers are connected with relays P and P respectively by means of circuits made resonant to the two signaling frequencies respectively by condensers 26 and 26, as shown. 1 The variations in the strength of the current from battery :23' are thus reproduced as alternations in relays S and S for the section are deenergized; the signal therefore indicates stop. As for the signal E for the sect-ion next in the rear, the lamp Y is illuminated, thus indicating caution, because relay S is deenergized, current from transformer T for this section being cut off at contact 10 of relay S for section I)E; relay S for section C-D, is however, energized because of the presence in the rails of this section of current from transformer T at the exit end of the section. The green lamp G of the signal for the second section in the rear (section BO) is illuminated because both relays S and S" for this section are energized; the signal E for this seetion, therefore, indicates proceed.

The operation of the vehicle carried signaling apparatus is as follows:

lVhen the vehicle V is in section A-B, which section is unoccupied except for vehicle V, both relays P and P on this vehicle are energized so that the green lamp G is illuminated, indicating proceed. As the vehicle enters section B--C, no change will occur because this section and the section CD in advance are unoccupied. When, however, the Vehicle enters section C-D, which is the'section in the rear of an occupied section, relay P will become, cle-energized because the signaling current to which this relay responds is not present'in the rails of the section; lamp G will therefore be extinguished and lamp Y will become illuminated 'so that the signal on the vehicle indicates caution. As the vehicle V enters section DE which is already occupied by vehicle V in advance of V, relay P will also become de-energized because of the absence of signaling current in the rails of this section so that lamp Y will become extinguislled and lamp R will be illuminated, indicating stop.

In Fig." 2 I have shown an alternative means for transmitting energy from the track rails to the apparatus on the vehicle. Instead of employing a coil in inductive relation to the rails as in Fig. 1, the resonant circuit a (corresponding too. in Fig. 1) is connected directly with the journal boxes or wheels of the front axle of the vehicle, the inductance of this axle and connecting wires 14 constituting the inductance of the resonant circuit a which corresponds to resonant circuit a of Fig. 1. The operation of the vehicle-carried apparatus when this modification is employed is the same as that of the apparatus of Fig. 1.

It is, of course, understood that the relays P and P on the vehicle may be employed to give signals of any desired character or to control the vehicle in any desired manner. If it is desirable t9 govern the speed of the vehicle in accordance with trafiic conditions in advance, such control. may be accomplished by means such as that shown in Fig. 3, wherein 27 is a contact arm operatively connected with the running gear of the vecluded in circuits with the contacts of relays l and P. A brake application magnet M is controlled by these circuits in the following manner. When both relays P and P are energized, the circuitfor magnet M is completed through the upper contact points of these relays and the fixed contact segment 28, which is of such length that the vehicle may proceed at maximum speed before the circuit will be opened by the movement of arm 27 beyond the right hand end of segment 28. When, however, relay P becomes de-energized and relay P is energized, this being the caution condition of vehicle carried apparatus, the circuit for magnet M is completed through the lower contact point of relay P and segment 29, which segment is shorter than segment 28, so that the vehicle must proceed at an intermediate speed in order to avoid opening the circuit of magnet M. .VVhen both relays l and P are de-energized, this being the stop condition of the apparatus, the circuit for magnet M is completed through the very short segment 30, so that if the vehicle exceeds a very low speed, the circuit for magnet M will be opened and the brakes applied. It is understood that so long as magnet M is energized, the brake pipe remains closed and the brakes are not applied. The three speeds corresponding to segments 28, 29 and 30 may be any desired values, such, for example, as 60, 30 and 10 miles per hour.

Referring now to' Fig. 4, the signaling system here shown is similar to that shown in Fig. 1 except as to the means for supplying the currents of the two signaling frequencies to the rails of each section. In this view, the two pairs of transmission means 3 and 3 are alternately connected with the rails of the successive block sec.- tions through transformers T and T, so that the rails of any one block section are directly supplied with current of only one frequency. In order to secure currents of both frequencies in each block section, I provide resonant transformer bonds N and N connected around the rail joints 2, each bond comprising a transformer whose primary is connected with the two adjacent sections of rail H and whose secondary is connected with a condenser as shown. Each.of these bonds is adjusted to resonance at the frequency of the current which is directly supplied to the forward of the two sections to which the bond is connected; that is, bond N at location B is resonant to the frequency of generator 4, bond N at location C is wro e? resonant to the frequency of generator 4,

etc. llt will be seen, therefore, that normally the current which is directly supplied to each section is freely transmitted to the section next in the rear, but cannot reach the second section in the rear because it is intercepted by a bond which offers a rela tively high impedance to current of that frequency.

Relays S and S are supplied with energy from the track rails exactly as in Fig. 1, the circuits for these relays being tuned as be fore, so that relay S responds only to current from a transformer T and relay S only to current from transformer T. It will be evident, therefore, that when a block section is occupied by a car or train, both relays connected with that section will be de-energized and only one relay for the section in the rear will be energized, depending on which frequency is directly supplied to such section in the rear. Because of this fact that one relay or the other may be energized to give a caution signal, the control of each signal E by the relays S and S is slightly different from that shown in Fig. 1. This control is such that if both relays are energized (as shown at location B) the circuit for the green, or proceed lamp, G, is closed through the upper contact points of each relay; if both relays are de-energized (as shown .at location D) the circuit for the red or stop lamp R is closed through the lower points of the contacts of both relays; whereas, if either relay is energized and the other de-energized, the circuit for the yellow or caution lamp is closed through an upper contact point of the energized relay and a lower contact point of the tie-energized relay. It is believed that the operation of these signal circuits will be obvious from this explanation and that no further detailed description is required.

The apparatuson the vehicle V- is exactly the same as that shown in Fig. 1, ex-

ceptv that the control of the vehicle-carried signal lamps G, Y and R by relays P and P is the same as that of each roadside signal l by the relays S and S.

The operation of the system shown in Fig. 4 will be obvious from the foregoing description of the structure, and from the explanation given hereinbefore of the operation of the system shown in Fig. .1. lltis apparent that when a section, as D-E, is occupied by a car or train, the red or stop lamp R of the signal for that section will be illuminated because both relays S and S for such section are de-energized; the yellow or caution lamp Y of the signal for the section C--D next in the rear is illuminated because relays S for this section is energized and relay S" de-energized; the

green or proceed lamp G of the signal for the second section in the rear (section lB-C) 25 I as' in Fig. 3. The operation of thisappara- -tus is as follows:

is illuminated because both relays for this section are energized. As the following vehicle V enters section CD, relay P will become de-energized because the rails of this section contain current from transformer T only, hence the green lamp G will become extinguished and the yellow lamp Y" will become illuminated. As the vehicle pro.

ceeds into the already occupied section D-E the other relay P will also become dener- 'gized because of the absence of signaling shown in Fig. 5, wherein the brake magnet M and the contact arm 27 and the fixed contacts with which it co-operates are the same When both relays P and P are energized, the circuit for brake magnet M is completed through the upper contact points of these relays and contact segment 28, so that the vehicle may proceed at -maximum speed without a brake application being incurred. \Vhe-n, however, relay P becomes de-energized, relay P remaining energized, the circuit for magnet M is closed through the upper point of contact 32 and lower point of contact 33 and segment 29, thus imposing an intermediate speed limit on the vehicle. If the relay P becomes de=energized and relay P remains energized, the circuit for magnet M is still completed through segment 29 but now passes through the upper point of relay contact 33 and the lower point of contact 32; the intermediate speed limit is thus imposed on the vehicle. hen both relays P and P become de-energized. the circuit for brake magnet M is closed through segment30. lower point of contact 33 and lower point of contact 32, so that a very low speed limit must be observed or a brake application will ensue.

\Vhile I have in Fig. 4 shown fixed or roadside signals F, F, etc. such signals may be eliminated entirely if so desired, because the movements of the carsor trains can be safely and satisfactorily governed by the apparatuson such cars or trains alone. In

the event of the elimination of these" fixed signals, the relay S and S and their connections with the'track rails can, of course,

also be eliminated, leaving no apparatus in the trackway other than the resonant bonds N and N and the transformers, etc.. for supplying signaling energy to the rails.

In lieu of generating'the high frequency currents at a central point by generators 4 and 4, as shown in Figs. 1 and 4, the high frequency current may be generated by ap paratus local to each block section, such as is shown in Fig. 6, utilizing as a source of energy an alternating current transmission line 3 of a usual commercial frequency.

In Fig. 6 I have shown means for. trans-. forming alternating current of a commercial low frequency into one. of high'frequency, and for impressing the high frequency cur-' rent upon the track rails for the purpose of actuating signals as hereinbefore described.

"I accomplish this transforming operation by -first rectifying the alternating current of low frequency and then utilizing the resulting direct current to excite a vacuum tube device connected to act as a generator of sustained oscillations, whose oscillating circuit is inductively coupled to the track rails.

To alternating current transmission line 3 is connected the primary of transformer T having three secondary windings T T and T T is of low voltage, and is for the purpose of constantly energizing the filaments 34, 34, of the vacuum tube rectifiers R and R T is likewise of'low voltage and isfor the purpose of constantly energizing the filament, 35 of the vacuum tube device R T is of high voltage and has its terminals connected to the plate terminals 86, 36, of the rectifiers R and R while the middle point of its Winding is connected to wire 37. A wire 38 is connected to one terminal of each ofthe filaments 34 of the heated filament, while the tube offers a practically infinite resistance to the flow of current in the opposite direction. It will be evident therefore that when the secondary T is energized by the primary 'I unidirectional fiow of current through the tubes will result, one tube permitting the passage of positive half waves, the other of negative half waves, thus rectifying the alternating current of the transmission line 3 into direct current. This rectified current is conveyed to the vacuum tube device R by means of wires 37 and 38, a condenser 39 being connected across the wires 37 and 38 for smoothing out the current as will be readily understood.

\Vire 38 is connected to the plate 40 of R while wire 37 is connectedto the filament 35. Interposed between the plate 40 and the filament 35 is a grid41 which is connected by wire 42 to resonant circuit-a comprising condenser 43 and the secondary of transformer 44. The primary of transformer 44 is in the direct current circuit formed by the conductors 37 and 38, plate 40 and filament 35 of R Tt will be evident, therefore, that oscillations in the resonant circuit a will produce an alternating difi'erence of potential between grid 41 and filament 35, which will cause a corresponding variation in the direct current from wire 38 to plate 40, filament 35, transformer 44 to wire 37. The relative direction of currents through transformer 4'4 is such that oscillations once started in the resonant circuit a are maintained; that is, an increase in current in the direct current circuit will induce current in the resonant circuit a which will cause a change in the potential difference between the grid and filament which will tend to limit the flow of current in the direct current circuit through R The resulting decrease in the current of the direct current circuit will induce an opposite impulse in the resonant circuit a which will tend to increase the current in the D. C. circuit through R resulting in sustained oscillations of a frequency determined by the constants of the circuits. Across the terminals of the primary of transformer 44 is connected a resonant circuit comprising condenser 46 and primary of transformer 45. The variation in potential across primary of transformer 44 will thus induce oscillations in the circuit of transformer 45, whose secondary is connected in a tuned circuit through condenser 47 to the track rails H and H. It will be evident, therefore, that the low frequency alternating current in the transmission line 3 is transformed into high frequency current by means of the hereinbefore described apparatus, and that the said current may be utilized in the track rails for controlling signals as described in Figs. 1 and 4.

The signaling system shown in Fig. 7 is similar to that shown in Fig. 4 in that identical means is employed for impressing the signaling currents upon the rails of each block section and that both frequencies of the'signaling currents are obtained in each block section by bridging the insulated joints 2 of each section; but in this embodiment of my invention each bond M and M" comprises a wire 48, an impedance coil 49,

, and a condenser 50 which are arranged in series, the terminals of the wire being connected to the rails of the two adjacent block sections upon opposite sides of the joints 2.

Each bond M and M is resonant to the frequency of the current which is directly supplied to the forward of the two sections as in the form shown in Fig. 4, whereby the currentwhich normally is directly supplied to,'each section is freely transmitted to the section next in the rear, but cannot reach the second section in the rear because it is intercepted by a bond M which offers a relatively high impedance to current of that frequency.

Tt will be noted that the system disclosed in Fig. 7 is without the roadside signals: shown in Figs. 1 and 4, the purpose of which is to avoid complexity of description, although T wish it to be clearly understood that the roadside signal may be used equally as well with this system as with the other systems.

The signaling device on the vehicle V of Fig. 7 is similar to that shown in Figs. 1 and 4, except that in lieu of amplifying the current for each of the relays l and P by a single amplifier K connected to the coil 14, the currents of each frequency are amplified independently of each other from the current in coil 14. This is accomplished by connecting to the terminals of the coil 14 a circuit including the wires 21 and 22 in series with which is a condenser 15 and the primaries 51 and 51 of a pair of transformers J and J the whole forming a circuit (1 tuned broadly to the mean of the two frequencies of the generators 4 and 4.

The secondaries 52 and 52 are identically electrically connected to the amplifiers K and K respectively for amplifying the current transmitted to the relays P and P, and it is, therefore, thought that an explanation of one will sutlice for the other.

The apparatus for amplifying the current for relay P consists of a device K comprising a vacuum tube or bulb 16 having mounted therein a filament 17,.a plate 19, and a grid 18 interposed between the filament and the plate. The filament 17 is constantly heated by a battery 20 to which is connected one terminal of the secondary 52 of transformer J and a condenser 53 which is connected across the terminals of the secondary 52, the remaining terminal of secondary 52 being connected to the grid 18. A. battery 23 is connected with the filament 17 and the plate 19 in such direction that a flow of current through the tube or bulb will result. owing to the electron emission from the heated filament 17. The oscillating difference in potential between grid 18 and the filament 17 serves to increase and decrease the rate of emission of electrons from the filament "and hence produces corresponding variations in the strength of current {lmving in the circuit of battery 23. The circuit of battery 23 includes the primary of a transformer 25, across the terminals of which is connected a condenser 24 to tune the transformer circuit to the frequency of its respective generator 4. The secondary of this transformer is connected with relay P by means of a circuit made resonant by the condenser 26. Thus it will be seen that the variations in the strength of the current from battery 23 are reproduced as alternations in the resonant relay circuit.

It will be 'manifest from the preceding descriptlon that in operation the coil 14 beingin inductive relation to the rails,

which are charged with the two signaling frequencies of the generators 4 and 4, the frequencies will be reproduced in the coil 5 14 and transmitted to the transformers of the circuit a. The secondary circuits of these transformers each being resonant to one of the two frequencies will select its respective frequency and convey the same through the apparatus to their respective relays]? and P to energize the latter for controlling the signals G, Y and R.

So far as the action of the track circuits under various traffic conditions, is concerned the operation is identical with that previously described of Fig. 4; therefore, it is thought that a description necessary.

While I have stated in the foregoing specification that the frequencies of the signaling currents in the track rails should be high, it will be clear that the effect of varying the frequency is an effect of degree only, in that the main purpose of these cur-' rents is tov induce voltages in the traincarried receiving circuits and the higher the frequency the higher is the induced voltage for a given current value. So far as concerns the practical embodiments of my invention, then, the frequencies of the signaling currents are immaterial, the only requirement being that for reasonable alues of currents in the track rails the voltages induced in the train-carried circuits shall be sufficient to reliably control the train 1 governing apparatus.- The *word high, therefore, as applied to these frequencies, 40 is used solely with respect to the-induction of suffi-cient voltage, and any frequency is high which accomplishes this. g It is thoughtfrom the foregoing, taken "in connection with the accompanying .drawings, that the construction. and operation of my devices and their modifications will be understood by those skilled in the art and that minor changes of constructionand arrangement of circuits may be made without departing from the spirit and scope of the appended claims.

Having thus described my invention, what I claim is: I H 1. A railway signaling system comprising trackrails divided into block sections, means for impressing on the rails of each section signaling currents differing in frequency, a relay for each section. receiving energy .from the rails thereof and responsive to signaling current of one of said frequencies for controlling the supply of current of the other frequency tothe section in the rear, a. railway vehicle, and signaling means on B said vehicle controlled by energy received from the track rails and selectively responof the same is untravel over the track; a circuit on the vesive to currents of said frequencies to give a plurality of. indications.

O 2. A railway signaling system comprising track rails divided into block sections, means for impressing on the rails'of each section signaling currents differing in frequency, means for each section controlled by traffic conditions therein for governing the sup, ply of signaling current of one frequency to the rails of the section in the rear, a railway vehicle, and signaling means on said vehicle controlled by energy received from the traclc rails and selectively responsive to currents of said frequencies to give a plurality of indications.

3. A railway signaling system comprising track rails, a source of high frequency oscillating signaling current, a circuit resonant to said current and connected with said track rails, a .railway vehicle, a circuit thereon arranged to receive energy from said track rails, a second circuit on the vehicle resonant to said current, amplifying means interposed between said vehiclecarried circuits, and vehiclegoverning means controlled by said second vehiclecarried circuit.

4. 'A railway signaling system comprising a source of low frequency alternating current, transmission mains connected with said source and extending along the railway, means located at intervals along the railway for transforming said current into high frequency oscillating current, means for impressing said latter current on the track r ails,. and signaling means controlled by the presence of said latter currents in the rails.

5. A railway control? system embodying a plurality of means for producing across the rails periodic currents of respectively different frequencies, train carried devices responsive respectively to said different periodic currents, a stop device held ineffective by one of said currents, and a speed control means rendered effective to produce a given speed by another current.

6. In a railway signaling system, in com-- bination: ,a railway track; means nullified by the presence of a train on a predetermined ,portion of the track for normally supplying periodic signaling current. to the track rails of the track for a predetermined distance in the rear; a vehicle adapted to hicle resonant at the frequency of said sig naling current and having a portion thereof disposed in inductive relation to thetrack rails a relay on the vehicle responsive only to currentof the frequency of said signaling current; and trafiic protecting means on the vehicle governedby said relay.

7. Railway trafiic controlling apparatus comprising track rails divided into block sections by insulated joints, means for eachsection controlled by traffic conditions in advance for impressing on the track rails thereof signaling currents of two different frequencies, a vehicle for travel on said rails, and means on said vehicle controlled by signaling currents in the track rails, and responsive to the presence of current of one of said frequencies only to give a caution indication, and to the presence of currents of both of said frequencies to give a proceed indication.

8. A railway signaling system comprising track rails, means for impressing thereon high frequency oscillating signaling currents of two frequencies, two circuits con trolled by energy in said rails and resonant respectively to said two frequencies, and signaling means controlled by said circuits.

9. Railway trailic controlling apparatus comprising track rails, a source of alternating signaling current connected thereto, a railway vehicle provided with an electron tube amplifier having a heated filament and a grid and a plate, a circuit on said vehicle inductively related to a track rail and including a capacity device, a grid circuit for said amplifier shunted by said capacity device,.a plate circuit for said amplifier including a source of direct current, and means associated with said plate circuit and responsive to variations in the strength of the current flowing therein for governing said vehicle.

10. Railway trafiic controlling apparatus comprising track rails, means for supplying alternating signaling current to said rails, a vehicle, a circuit on said vehicle including a winding in inductive relation with a track rail and a capacity device, an electron tube amplifier on said vehicle having its grid and filament connected across said capacity device, a plate circuit for said amplifier including a source of direct current, and means associated with said plate circuit and responsive to variations in the strength of the current flowing therein for governing said vehicle.

11. Railway trafiic controlling apparatus comprising track rails, means for impressing two alternating signaling currents thereon, a vehicle provided with means for inductively receiving voltages due to said currents, and speed governing apparatus on said vehicle controlled by said voltages for permitting high speed when both currents are present in the track rails, an intermediate speed when only one current is present, and a low speed when both currents are absent.

12. Railway trafiic controlling apparatus comprising a trackway divided into sections, means for constantly impressing an alternating signalingcurrent on the rails of each section, means for each section controlled by traiiic conditions in advance for impressing on the rails thereof a second alternating signaling current, a vehicle provided with means for inductively receiving voltages due to said currents in the track rails, and apparatus on said vehicle controlled by said voltages for automatically governing the speed of the vehicle.

13. Railway traffic controlling apparatus comprising track rails, means for impressing two alternating signaling currents thereon, a vehicle provided with means for inductively receiving voltages due to said currents, amplifying means on said vehicle controlled by the voltages impressed on said receiving means, and speed governing apparatus on said vehicle controlled by said amplifying means for permitting high speed when both currents are present in the track rails, an intermediate speed when only one current is present, and a low speed when both currents are absent.

14:. Railway traiiic controlling apparatus comprising a trackway divided into sec-- tions, means for constantly impressing an alternating signaling current on the rails of each section, means for each section controlled by trafiic conditions in advance for impressing on the rails thereof a second alternating signaling current, a vehicle provided with means for inductively receiving voltages due to said currents in the track rails, amplifying means on said vehicle controlled by the voltage impressed on said receiving means, and speed governing apparatus on said vehicle controlled by said amplifying means.

15. Railway trailic controlling apparatus comprising a trackway divided into block sections, a vehicle for travel thereon, a circuit on the vehicle, means located in the trackway for creating an alternating potential in said circuit, a second circuit on the vehicle including a source of direct current, amplifying means on the vehicle controlled by the alternating potential in the first circuit for causing variations in the strength of the current in said second circuit,

a transformer whose primary is supplied with current from said circuit, a relay responsive to alternating current having a winding supplied with current from the secondary of said transformer, and vehicle governing means controlled by said relay.

16. Railway tratlic controlling apparatus comprising a traclrway, a vehicle for travel thereon, a circuit on the vehicle including a condenser, means located in the trackway for creating alternating signaling current in said circuit; an electron tube amplifier on said vehicle comprising a heated filament, a plate and a grid; the terminals of said condenser being connected with said filament and said grid respectively, a plate circuit for said amplifier, and vehicle governing means controlled by the current in said plate circuit.

10 output circuit of said amplifier.

18. Railway traflic controlling apparatus comprising track rails, a source of alternating signaling current connected thereto, a railway Vehicle provided with a receiving circuit inductively related to a track rail and including a capacity device, an amplifier on the vehicle having an input circuit shunted by said capacity device, and means controlled by the output circuit of said amplifier for 20 controlling the brakes of said vehicle.

19. Railway traffic controlling apparatus comprising track rails, a source of alternating signaling current connected thereto, a railway vehicle provided with a receiving circuit inductively related to a track rail and tuned by acondenscr, and governing means on the vehicle controlled by the alternating difierence of potential across said condenser.

20. Railway traflic controlling apparatus comprising track rails, a source of alternating signaling current connected thereto, a railway vehicle provided with a receiving circuit inductively related to a track rail and tuned by a capacity device, an amplifier on the vehicle having an input circuit shunted by said capacity device, and governing means on the vehicle controlled by the output circuit of said amplifier.

21. Railway traflic controlling apparatus comprising track rails, a source of alternating signaling current connected thereto, a railway vehicle provided with a receiving circuit inductively related to a track rail and tuned by a capacity device, an electron tube amplifier on said vehicle, a grid circuit for said amplifier shunted by said capacity device, a plate circuit for said amplifier, and governing means for said vehicle controlled by said plate circuit. 22. Railway trafiic controlling apparatus comprising track rails, means for impressing .an alternating signaling current thereon, a railway vehicle provided with a receiving circuit inductively relatedto a track rail and including a capacity device, .and governing apparatus on said vehicle shunted by said capacity device. r

23. Railway traflic controlling apparatus comprising a trackway, a vehicle for travel thereon, a circuit on said vehicle including a capacity device, means located in the trackway for creating alternating signaling cur rent in said circuit, and governing apparatus 011; said "vehicle shunted by said capacity device.

24. Railway trafiic controlling apparatus comprising a trackway, a vehicle for travel thereon, a circuit on the vehicle including a condenser, means located in the trackway for creating alternating signaling current in said circuit; and vehicle governing means controlled by the alternating difference of potential across said condenser.

25. Railway traflic controlling apparatus comprising a trackway and a vehicle for travel thereon, a tuned circuit on said vehicle including a condenser, means located in the trackway for creating alternating signaling current in said circuit, and vehicle governing means of said vehicle controlled by the alternating difference of potential across said condenser due to said signaling current.

26. Railway trafiic controlling apparatus comprising track rails divided into block sections, a vehicle for travel thereon, means for each section for constantly impressing signaling current of one frequency on the rails thereof, means for each section controlled by traflic conditions in advance for impressing signaling current of another frequency on the rails of the section, and means on said vehicle controlled by signaling currents in the track rails and responsive to the presence of current of the first-mentioned frequency only to give a caution indication and to the presence of currents of both of said frequencies to give a proceed indication.

27. Railway trailic controlling apparatus comprising a trackway and a vehicle for travel thereon, a receiving circuit on the vehicle, means in the trackway for creating I alternating potentials differing in frequency in said circuit, a second circuit on said vehicle including a source of direct current, an amplifying device controlled by the composite alternating potential in said receiving circuit for causing similar composite variations in the strength of the current in said second circuit, a third circuit and a fourth circuit on said vehiclereceiving current from said second circuit and tuned to resonance respectively at the frequencies of the two potentials created in said receiving circuit, and vehicle governing means controlled by currents in said third and fourth circuits.

28. Railway trafiic controlling apparatus comprising track rails and a vehicle for travel thereon, means for impressing on said track rails two alternating signaling currents differing in frequency, a receiving circuit on said vehicle in which is created a composite alternating potential due to said alternating currents in the rails, a second circuit on said vehicle including a source of direct current, an amplifying device controlled by the composite alternatlng potential in said receiving circuit for causing similar composite variations in the strength of the current in said second circuit, means on the vehicle for selectively disassociating the two components of the current variations in said second circuit corresponding in frequency to the two signaling currents in the track rails, and vehicle governing means con trolled by said two component currents.

29. Railway traffic controlling apparatus comprising track rails anda vehicle ,for travel thereon, means for impressing on said track rails two alternating signaling currents differing in frequency, a receiving circuit onsaid vehicle in which is created a I composite alternating potential due to said alternating currents in the rails, a second circuit on said vehicle including a source of direct current, an amplifying device controlled by the composite alternating potential in said receiving circuit for causing similar composite variations in the strength of the current in said second circuit, two transformers on said vehicle the primary of each transformer being included in said second circuit, secondary circuits for sald transformers tuned to resonance at the frequencies of said two signal ng currents respectively,

and vehicle governingmeans controlled by the currents'in said secondary circuits.

30. Railway trafiic controlling apparatus comprising track rails and a vehicle for I travel thereon, means for impressing on said track rails two alternating signaling currents differing in frequency, a receiving circuit on said vehicle in which is created a composite alternating potential due to said signaling currents in therai'ls; an elec= tron tube on said vehicle comprising a heated filament, a plate and a grid; said filament and said grid being connected with said receiving circuit, a 'plate circuit for said tube including a source of direct ourrent, whereby. the composite alternating l the track rails of each block and controlled of the vehicle for brakes.

by traffic conditions in advance for transinitting proceed and caution indications from the track rails to a vehicle by induction, and means on the vehicle controlled jointly by said indications and by the speed governing the vehicle 32. In combination, a railway track divided into blocks, means associated with the track rails of each block and controlled by trafiic conditions in advance for transi i as? mitting proceed and caution indications from the track rails to a vehicle by induction, and means on the vehicle controlled by said indications and by the absence thereof for imposing difierent fixed speed limits on the vehicle.

33. lin combination, a railway track divided into blocks, means associated with the track rails of each block and controlled by traffic conditions invadvance for transmitting proceed and caution indications from the track rails to a vehicle by induction, and means on the vehicle responding to the caution indication by applying the brakes if the speed is above a given value, and to the absence of both indications by applying the brakes if the speed is above a second and lower value.

84. Railway traflic controlling apparatus comprising a stretch of track divided into successive track sections, line wires along said stretch supplied with energy, and

means including an electron tube for each 7 section supplied with energy from said line wires for supplying energy to the rails of the associated section 35. Railway traflic controlling apparatus comprising a stretch of track divided into successive track sections, line wires along said stretch supplied with energy, and an electron tube, for each section connected with said line wires for supplying energy to the associated section.

36. Railway traffic controlling apparatus comprising a stretch of track divided into successive track sections, line wires along said stretch supplied with energy, an electron tube for each section, means for supplying the grid of each such tube with periodic energy from certain of said line wires, and means controlled by each tube for supplying high frequency energy to the associated section.

87. In combination, divided 'intosections, a local generator'oi alternating current for each section, and means including line wires extending along said track for. energizing all of said generators from a common point.

88. In combination, a, railway 'track divided into sections, a local electron tube generator of alternating current for each section, and means including line wires extending along said track for energizing all of said generators from a common point.

39. lln icombin'ation, a railway track divided into "sections, a local electron tube generator of alternating current for each section, and means including line wires extending along said track for supplying the filaments and plate circuits of said tubes from a common point.

40. The method of governing railway traflic which consists in producing in the track railsa flow of periodic current, and

a railway track A lllll ire governing the movement of a vehicle jointly by a centrifuge responsive to its speed variations and by said current in ,the track rails. 41. A railway traflic controlling system 5 comprising trafiic controlling apparatus carried on a railway vehicle and arranged to govern its movement and selectively responsive to currents of different frequencies in the track rails, and means for supplying the track rails with currents of said dif-' 10 ferent frequencies at respective successive points without superposing current of wrong frequency at any given point.

In testimony whereof I afiix my signature.

LLOYD V. LEWIS. 

